RESUMO
CD4+CD56+ lineage negative malignancy has recently been considered as plasmacytoid dendritic cell (PDC) leukemia/lymphoma. We investigated immunophenotypic and functional characterizations of PDC leukemic cells in one case. Lineage markers were all negative except partially positive CD11c and positive CD117, indicating malignant cells were leukemic PDCs coexpressing myeloid and progenitor cell surface antigens. Leukemic PDCs cultured with IL-3 increased in size and expression of CD11c, CD40 and HLA-DR, although the cells cultured with IL-2 or GM-CSF showed little proliferation. Furthermore, CD40 ligation after IL-3 stimulation yielded morphological changes such as expression of dendritic process. These findings showed that malignant cells were consistent with leukemic PDCs. However, secretion of interferon-alpha was not detected in leukemic PDCs with the stimulation of CpG ODN or inactivated herpes simplex virus-1.